Patent GB-652839-A (GB)
Title: Blended rubber latex frothed sponge
IPC: D06N3/04
Filed: 1948-11-18
Abstract: A frothed latex sponge comprises at least 70 per cent by weight of a rubber latex and not more than 30 per cent by weight of a resin latex obtained by polymerizing a mixture of 80 to 95 per cent by weight of a vinyl aromatic monomer and 20 to 5 per cent by weight of a diene hydrocarbon monomer.  The term rubber latex includes natural latex, polychlorprene latex, butadiene-styrene, and butadiene-acrylonitrile copolymers and their mixtures.  The preferred resin latex is obtained from styrene and butadiene. Specified dienes include butadiene, isoprene, 2,3-di-methyl butadiene, 1,3-dimethyl butadiene, pentadiene-1,3; pentadiene-2,4; 3-methyl-pentadiene-2,4; 3,4-di-methyl pentadiene-2,4; straight and branched chain hexadienes and heptadienes.  Specified vinyl aromatics include styrene, m- and p-chlorostyrene, dichlorostyrenes and alkyl styrenes, e.g. methyl and isopropyl styrene, and vinyl naphthalene.  Emulsion polymerization is effected wherein a styrene phase including a modifier and styrene reacts with butadiene in the presence of a water phase containing a catalyst and emulsifier.  Catalysts specified are potassium persulphate, benzoyl peroxide, hydrogen peroxide, perborates and percarbonates, 0.01 to 1.0 per cent by weight being used. Emulsifiers, 1.5 to 10 per cent by weight, specified are fatty acid soaps, e.g. sodium stearate, and resin acid soaps, e.g. sodium resinate.  Copolymerization is effected between 20 DEG  and 70 DEG C. for 4 to 100 hours.  The usual accelerators and antioxidants are added to the rubber latex and other materials which may be added are thickening agents, e.g. casein, gum tragacanth and water glass, and modifiers, e.g. castor oil (for elasticity) carbon blacks (loading agents), magnesium oxide and calcium silicate (strengtheners), paraffin wax (improves rebound properties) and various dyes and colouring materials.  The products are useful for furniture, car seats, under rug mats and shoe liners.  In example 6, the rubber latex is a mixture of natural and a synthetic rubber from the copolymerization of 70 parts butadiene and 30 parts of styrene.ALSO:A frothed latex sponge comprises at least 70 per cent by weight of a rubber latex and not more than 30 per cent by weight of a resin latex obtained by polymerizing a mixture of 80 to 95 per cent by weight of a vinyl aromatic monomer and 20 to 5 per cent by weight of a diene hydrocarbon monomer.  The term rubber latex includes natural latex, polychloroprene latex, butadiene-styrene and butadiene-acrylonitrile copolymers and their mixtures.  The preferred resin latex is obtained from styrene and butadiene. Specified dienes include butadiene, isoprene, 2,3-dimethyl butadiene; 1,3-dimethyl butadiene; 2-ethyl butadiene; pentadiene-1,3; pentadiene-2,4; 3-methyl pentadiene2,4; 3,4-dimethyl pentadiene-2,4; straight and branched chain hexadienes and heptadienes.  Specified vinyl aromatic monomers include styrene, m- and p-chlorostyrene; dichlorostyrenes and alkyl styrenes, e.g. methyl- and isopropyl styrene, and vinyl naphthalene.  Stabilizers which can be added are ammonia, alkali metal hydroxide, potassium oleate soap, rosin soaps, sodium stearate, potassium lauryl sulphate, sulphonated hydrocarbons or sodium alkyl naphthalene sulphate. Thickening agents may be added, e.g. casein, gum tragacanth and water glass; antioxidants, e.g. phenyl-b -naphthylamine, di-b -naphthyl-p-phenylene diamine and the heptyl-diphenylamines; and accelerators, e.g. zinc mercaptobenzothiazolate, zinc diethyldithio carbamate, benzothiazyl disulphide and tetramethyl thiuram disulphide are then added; and a modifier such as castor oil, carbon black, magnesium oxide, calcium silicate, paraffin wax, dyes and colouring materials may also be added.  In an example, natural rubber is slowly agitated with potassium oleate solution; ethylzincate, a paraffin wax coated dispersion of zinc mercaptobenzothiazolate and sym-di-b -naphthyl-p-phenylene diamine then added and the mixture matured.  An aqueous dispersion of sulphur, potassium rosinate and paraffin wax are added and agitated.  To this compounded rubber latex, a resin latex is added and the whole frothed, then a dispersion of zinc oxide and diphenyl guanidine is added.  Subsequently a dispersion of sodium silicofluoride is added and the whole poured into a mould and gelled. In example 6, the rubber latex comprises a mixture of natural and a synthetic rubber (butadiene-styrene).  The Specification as open to inspection under Sect. 91 comprises also the addition of more than 30 per cent by weight of the resin latex.  This subject-matter does not appear in the Specification as accepted.